Redox Reactions
An element can have several oxidation numbers , based on reactivity , excitation and Group Number . Highest Oxidation Number : For s-block : Group Number For p-block : Group Number - 10 Oxidation ----> Loss of Electron (Remember 'O' of Oxidation stands for "Loss" ) Redox -----> Gain of Electron Oxidizing agent increases the other element's oxidation state , while itself undergoing reduction . The opposite is applicable for Reducing Agent . Oxidation States of Elements Note : The positive oxidation states show ionic bonding while negative oxidation state shows covalent bonding in Metals . In Non Metals , the positive oxidation shows covalent bonding while negative shows ionic bonding . Covalent Bond will never proceed oxidation number +4 or -4 . Hydrogen (1) +1 | -1 Lithium (3) +1 Berylium (4) +2 Boron (5) +1 +2 +3 Carbon (6) +4 +3 +2 +1 | -1 -2 -3 -4 Nitrogen (7) +1 +2 +3 +4 +5 | -3 -2 -1 (Nitrogen forms ionic as well as covalent bond ; ionic will result in gain of maximum 3 electrons (Reduction ) covalent will result in loss of maximum 5 electrons (oxidation) ) Oxygen (8) +2 +1 | -1 -2 Fluorine (9) -1 Sodium (11) +1 | -1 Magnesium (12) +2 +1 Aluminium (13) +3 +2 +1 | -1 -2 Phosphorous(14) +5 +4 +3 +2 +1 | -1 -2 -3 Sulphur (15) +6 +5 +4 +3 +2 +1 | -1 -2 Chlorine (17) +7 +6 +5 +4 +3 +2 +1 | -1 Potassium (19) +1 | -1 Calcium (20) +2 +1 | -1 Chromium (24) +6 +5 +4 +3 +2 +1 | -1 -2 -4 Manganese (25) +7 +6 +5 +4 +3 +2 +1 | -1 -2 -3 Iron (26) +6 +5 +4 +3 +2 +1 | -1 -2 Copper (27) +1 +2 +3 +4 Zinc (28) +1 +2 Important Notes :-''' '1) Noble Gases : Expected Oxidation Number is 0 due to unreactive nature . But , ' ' Krypton(36) shows +2 ; Xenon (54) shows +2 +4 +8 +10 ; Radon(86) shows + 2 +6 . ' ''' Helium , Neon and Argon show 0 oxidation state . 2) All Metalloids show -4 -3 -2 -1 | +1 +2 +3 +4 Oxidation states . Carbon(6) , Silicon(14) , Arsenic(32) , Tin(50) , Lead(82) are metalloids belonging to Group 14 . Oxidation States of some Groups CN -1 SO4 -2 OH -1 N3H -----> Hydrozoic Acid H2SO5 -------> Caro's Acid H2S2O8 ------> Perosulphuric acid or Marshall's Acid Metal with Carbonyl Group (CO) has 0 oxidation number . For removal of one mole , 1 Farad current is needed . 1 Farad = 96500 Couloumb (From Electrochemistry) Types of Redox Reaction Combination : X + Y ------> Z Decomposition : Z -------> X + Y Displacement : XY + Z -------> X + ZY Disproprtionation : '''The oxidation State of a single reactant changes into two other oxidation states in the products . '''e.g. Cl2 + H2O -------> HCl + HOCl ' 0 +1 -2 +1 -1 +1 -2 +1' Here , Chlorine has two oxidation states in the products section ---> -1 and +1 . K2Cr2O7 and KMnO4 are the most important oxidizing agents . K2CrO7 in acidic medium -----> Oxidition State of Chromium =+ 3 ... For Cr2 =+ 6 (Exchange of 6 electrons) KMnO4 in acidic medium ------> Oxidation State of Manganese =+ 2 (Exchange of 5 electrons ) KMnO4 in basic medium --------> Oxidation State of Manganese =+ 4 (Exchange of 3 electrons ) Equivalent Weight ' Molecular Weight Equivalent Weight = ---------------------------------------------------- No. of electrons gained or lost ' Category:JEE